Typically, in the field of semiconductor manufacturing, even if there are two identical integrated circuits on the same die, each integrated circuit would still be unique because of physical randomness even though the two integrated circuits are manufactured using the same manufacturing process and the same material. This inherent variation may be extracted and used as unique identifications and can be thought of as being similar to DNAs of human beings. The physically unclonable function (PUF) has been proposed and became popular to provide security and uniqueness to integrated circuits. A PUF is based on a cryptography which is easy to evaluate and would produce an output, but such output could be hard to predict. Each PUF circuit may provide a unique identity and a unclonable function based on static variations in the components that are used to manufacture the device, and such variations are rarely the same for two electrical components such that the variations would be used to provide a unique identity to each PUF circuit.
In a delay based PUF device, the identity of the device could be generated based on the delay chains of logic which is less secure, and it could be difficult to distinguish among devices by using the variations of the delay chains. A Static Random-access memory (SRAM) PUFs may generate such variations during a startup stage, but to do so may cause time delays during power on or power off. Also, using additional circuits may increase power consumption, may require extra bits, and may require a filtering mechanics to identify the bits that could be masked.
In addition, because PUF devices are inherent as technologies continue to develop even though foundries have kept attempting to control the variations of the core devices, it could be desirable to actually develop a PUF device that has a maximum static variation for certain applications in this technical field.